(1) Field of the Invention
The present invention relates to a screen printing machine which is used to print a wiring pattern or the like on a substrate, for example, such as a substrate for a thick film integrated circuit, a print substrate, etc., and more specifically, to an improvement in a screen printing machine comprising an adjusting means for a substrate position for preventing a dislocation of printing and a recognition means.
(2) Prior Art
In prior art, the adjustment of position of a substrate in a screen printing machine of this kind has been made by carrying out a rough positioning on the basis of an end face of the substrate or a hole made in the substrate, thereafter causing the substrate to be attracted to an attraction table, and displacing the attraction table in a direction of X, Y and .theta., thus achieving the adjustment of position with high accuracy. Specifically, a substrate position adjusting means as disclosed in, for example, such as Japanese Utility Model Application Laid-Open No. 54-124968 Specification has been proposed.
According to the above-described conventional screen printing machine, the machines uses, as a base board, a table 1 which is rotatable in a direction of .theta. on which is placed a substrate which is a material to be printed, as shown in FIG. 2. An X-Y moving means is constituted by a first moving base 2 for moving the table 1 in a direction of X, a first linear motion mechanism 3 for linearly guiding and moving the first moving base 2 in a direction of X, a second moving base 4 for moving the first moving base 2, which moves the table 1 in the direction of X, in a direction of Y, and a second linear motion mechanism 5 for linearly guiding and moving the second moving base 4 in a direction of Y. The table 1 is displaced along with the X-Y moving means in the direction of X, Y and .theta. whereby the adjustment of position of the substrate on the basis of an alignment mark provided on the substrate is accomplished.
The recognition means for the substrate position in the screen printing machine has been proposed which uses a recognition camera, as disclosed in, for example, such as Japanese Patent Application Laid-Open No. 57-75889 Specification.
However, the above-described substrate position adjusting means in the screen printing machine requires mechanisms which individually displace those as described above in the direction of X, Y and .theta., respectively, and in addition, said means is of a 3-layer construction. For this reason, the entire mechanism becomes large-sized to impede space-saving and light-weighting, and the rotational motion mechanism for the table becomes complicated in construction as compared with the linear motion mechanism.
On the other hand, the conventional substrate position recognition means in the screen printing machine uses only one unit of a recognition camera, and said camera is fixedly provided. Therefore, for confirmation of the position of a substrate on the table, there is only one check point, which results in the insufficient printing accuracy.
In view of the foregoing, two or more check points may be provided in order to improve the accuracy of printing as desired. However, this requires more than two recognition cameras, thus considerably increasing the cost of the machine.